Linkage for drawing press



Jan. 18, 1966 E. BERGMANN 3,229,535

LINKAGE FOR DRAWING PRESS 7 Filed Oct. 19, 1961 4 Sheets-Sheet l INVENTOR EwAw 3572a M4NN BY Mf ATTORNEYS Jan. 18, 1966 E. BERGMANN 3,229,535

LINKAGE FOR DRAWING PRESS Filed Oct. 19, 1961 4 Sheets-Sheet 2 INVENTOR E mu. E1accr14/wv BY W W ATTORNEYS Jan. 18, 1966 E. BERGMANN 3,229,535

LINKAGE FOR DRAWING PRESS Filed Oct, 19, 1961 4 Sheets-Sheet 5 INVENTOR EwAm IBEPQMAMV BY m and ATTORNEYS 1966 E. BERGMANN LINKAGE FOR DRAWING PRESS 4 Sheets-Sheet 4 Filed Oct. 19, 1961 ZNVENTOR BEEGMANN I ENAL-D ATTORNEYS United States Patent 3,229,535 LLWKAGE FOR DRAWING PRESS Ev ald Bergmann, Goppingen, Wurttemherg, Germany, assiguor to L. Schnler A.G., Goppingen, Wurttemberg, Germany, a firm Filed Oct. 19, 1951, Ser. No. 146,310 Claims priority, application Germany, Oct. 22, 1960, Sch 28,651 Claims. (Cl. 74-38) This invention relates to a linkage for a drawing press. In the operation of a drawing press it is desirable that the tool should make contact with the blank at relatively low speed and then descend to the bottom dead centre at uniform or increasing speed, ascending again at relatively high speed to complete the idle stroke quickly. For achieving these different speeds, the pitman connecting the driving crank or eccentric with the ram is divided in a known type of press into two arms hingeably connected to form a toggle or knee joint.

The hinge connecting the two pitman halves is deflected by special drive means transversely to the line connecting the crank and the ram, thus superimposing upon the sinusoidal motion of the pitman a supplementary motion generated by the lateral deflection of the hinge. In a known press a link rod driven by a separate crank is articulated with the hinge of the toggle or knee arms. Meshing gears which have like numbers of teeth may be keyed to the two crankshafts.

A common feature of the drive means of known drawing presses is that the supplementary motion modifying the sinusoidal motion generated by the crank is always directly imparted to the knee arms at or in the immediate vicinity of the hinge. The greater the lateral deflection of the hinge, the greater is the deviation from the motion generated by the rotating crank. However, the greater the hinge deflection for achieving a compound motion of a particular kind, the larger must be the crank used for the lateral hinge deflection and the longer must be the link coupling this crank with the hinge. This gives rise to grave structural difiiculties and leads to an enormous amount of space being wasted. Even if the hinge is not directly laterally deflected by a link and a crank, the linkage required for a sufliciently wide amplitude of deflection is still very large. The provision of large driving members and links cannot be avoided.

Toggle-jointed ram motions are known in which the arm which pivots on the crank or eccentric is rearwardly extended beyond its pivot on the crank pin and the extended slightly off-angled end is articulated to a link which oscillates about a fixed fulcrum. In these motions there is no special drive means for generating the transverse deflection but merely a guide means which, being stationary in relation to the transverse motion generated by the crank, imparts a supplementary transverse motion to the hinge which is likewise a sinusoidal motion. However, the phase of this motion is in quadrature to the longitudinal sinusoidal motion of the hinge.

The compound motion resulting from the combination of the two motions is further modified by a transverse motion due to the fact that the knee arm extension is guided along a circular path by the oscillating link. However, this modification merely slightly distorts the transverse motion due to the crank, it does not substantially change it. In this arrangement the arm which is pivotably attached to the crank forms a lever which transforms the amplitude of the transverse motion because the link guides substantially only in the longitudinal direction.

Calculation shows that these linkages which comprise only one crank and generate a guided reciprocation along a circular path are in principle incapable of providing the desired ram motion.

In order to achieve the required motion the application "ice of a more complicated transverse motion to the hinge than that described above has been found to be necessary. This explains the replacement of the simple motion generated by an oscillating link by special drive means of the kind already discussed.

The present invention concerns drive means for rams comprising a knee joint in which the transverse deflection of the hinge is not generated by guiding the end of one of the arms along a circular path. The invention consists in that a supplementary transverse motion other than one generated by guiding a knee arm along a circular path is impressed upon the joint at a point located at a distance from the hinge which is less than twice the length of said arm, so that the latter provides a lever transmission for amplifying said transverse motion.

A special advantage afforded by the invention is that the knee arm which works on the crank serves two purposes: on the one hand, the arm transmits the drive from the crank and, on the other, it provides a lever transmission which amplifies the supplementary transverse motion. This feature permits the drive means for the generation of the transverse motion to be substantially more. compact, and in presses which have an overhead drive the head of the press can be much smaller. Such a press is therefore not so top heavy.

In forms of construction based upon the present invention the knee arm which is pivotably connected with the crank will therefore normally be provided with three hinged connections. The arm itself may be straight or alternatively it may be cranked, the latter arrangement ofiering further possibilities for reducing the size of the press drive.

Another advantage of the invention is that the driving crank in any embodiment of the invention may be relatively small, the crank possibly being replaced by an eccentric. Finally, no difliculties are encountered in overcompensating any reduction in the length of the crank arm by a corresponding increase in the amplitude of the transverse motion, and this can be done without using bulkier transmission members for generating the larger amplitude.

The member for laterally deflecting the knee arm may be linked with the arm at a point between the crank and the hinge of the knee joint. However, in preferred embodiments of the invention the knee arm is rearwardly extended beyond the pivot pin of the crank to form a two-armed lever, and the supplementary drive means are linked to the extension representing the second lever arm. The knee arm which thus forms a two-armed lever may be cranked in the vicinity of its pivot point on the crank.

It will be understood that the following description of the particular arrangement of the transmission members in the proposed linkage is merely intended to clarify the kinematics of the proposed system and is not intended to limit the actual form of construction of individual members. For instance, a bell-crank lever might be embodied in a pivoted triangular plate or the like.

For achieving the desired optimal motion of the ram the hinge of the knee joint will not normally move in an elliptic or quasi-elliptic path, but in some other path which more readily permits the desired motion of the ram to be generated. The drive means provided for the lateral deflection of the hinge may themselves be even smaller than the lateral deflections impressed upon the knee arm by the crank because the supplementary motion impressed upon the arm will be amplified in the ratio of the two lever arms formed by the arm and its extension.

In certain embodiments of the invention the motion for the lateral deflection of the hinge may be derived from a special drive means rotating in synchronism with the crank. Preferably this drive means may be partly identical with the drive means provided for driving the blank holder slide, a possibility which permits a further saving in the number of driving parts.

Another feature of the invention consists in driving the blank holder through a linkage comprising three joints. This permits the blank holder slide to be kept substantially stationary for the duration of the entire drawing process, special cam means not being required.

Other features of the invention will emerge in the course of the following description of embodiments of the invention shown in the drawings and they will form the subject matter of claims. These features may be severally or jointly incorporated in the embodiments of the invention.

The drawings show forms of construction of drive means for the ram of a drawing press in schematic representation.

FIGS. 1, 2 and 3 are different embodiments of the inventive drawing press linkages;

FIG. 4 is the embodiment shown in FIG. 2, supplemented by a form of construction of drive means for the blank holder slide; and

FIG. 5 is a modification of the arrangement illustrated in FIG. 3.

In the embodiment of the invention schematically shown in FIG. 1 the motion of a crank 2 of a crankshaft 1 is indicated by a dotted circle 3. One arm 4 of a knee joint is pivoted on the pin of crank 22, whereas a second arm 6 of the joint is pivotably attached to a ram (not shown) at point 7, a hinge of the joint being indicated at 5. Numeral 31 denotes a guide for the ram, known in the art of drawing presses.

Arm 4 which is attached to crank 2 is extended beyond its pivot 8 on the crank to form a lever arm 9 which at its end 12 remote from the hinge 5 is hingeably attached to a link 13. The other end 14 of this link is articulated with an arm 15 of a two-armed lever 15, 16 movable about a fixed fulcrum 17. The end 18 of the other arm 16 is hingeably connected by a further link 19 with pin 8 of the crank. Lever arm 9 and link 19 together act in the fashion of a toggle joint.

The motion of the drawing ram can be varied by modifying the curve which defines the path of hinge 12. This curve can be readily varied by pivotably attaching link 19 to a different point 33 on the crank or to a selected .point 34 on the extension 9 of knee arm 4, said link being responsible for a kind of kinetic feedbac Finally, as shown in FIG. 2, instead of link 19, a disc cam may be keyed tocrankshaft 1 for driving hinge 18 of the two-armed lever 15, 16 and hinge 12 in conformity with a selectable kinetic programme.

The embodiment illustrated in FIG. 3 differs from. that in FIG. 1 substantially in that link 19 which is hinged at 18 is driven by crankshaft 1 through a separate crank 20, the motion of this crank being indicated by a circle 36. Moreover, in the embodiment according to FIG. 3, the two-armed lever 15, 16 is a bell-crank lever. Arm 4 of the joint and its extension 9 are likewise more or less cranked.

It will be readily understood that the several twoarmed levers may be straight or cranked according to the demands of the envisaged design. Assuming that the crankshaft 1 revolves at uniform speed, the two embodiments according to FIGS. 1 and 2 both generate a ram motion which very considerably approximates the desired ideal ram motion in a drawing pness.

FIG. 4 differs from FIG. 3 substantially only in that a separate linkage is shown for the actuation of a blank holder slide (not shown). The two-armed lever 15, 16 here has a third lever arm 21 pivotally connected by a link 22 with one end of a bell-crank lever 23, 24 which oscillates about a fixed fulcrum 25. Arm 24 of lever 23, 24 is pivotably connected by a link 26 with the end of one arm 27 of another two-armed lever 27,

28, likewise moving about a fixed fulcrum which, in the illustrated example, coincides with the axis of crankshaft 1. A pitman 29 for actuating the blank holder slide is articulated to the end of lever arm 28. Numeral 32 denotes a conventional guide for the blank holder slide.

The bell-crank levers comprised in this blank holder motion may likewise have arms set at different angles. The two links 22 and 26 and the pitman 29 all for-m knee-joint arms. The embodiment illustrated in FIG. 4 comprises three such joints which pass consecutively through their respective dead centres so that the blank holder remains at rest. This period of rest begins be fore the drawing plunger makes contact with the blank and ends after the plunger has been withdrawn, or immediately before it leaves the die.

FIG. 5 is a modification of the embodiment according to FIG. 3, so designed that, at the bottom dead centre of the ram, levers 13 and 15 are fully extended. This form of construction may be so arranged that when the ram fulcrum 7 is at bottom dead centre the two arms 4 and 6 will not be fully extended. That portion of the pressing thrust which is not taken up by shaft 1 is transmitted in this case by the fully extended hinge between link 13 and arm 15 to a bearing fulcrum 30 of the two-armed lever 15, 16.

However, in a particularly useful embodiment of the invention the linkage is so designed that, when arm 15 and link 13 are relatively fully extended, the knee joint arms 4 and 6 will likewise be close to or in their fully extended positions. Furthermore, the distribution of forces in the driving members will be optimal if, at bottom dead centre of the ram, not only the arms 4 and 6 and the hinge between arm 15 and link 13 are fully extended but at the same time the crank 2 is also at bottom dead centre.

The arrangement may further be such that arm 15 and link 13 swing slightly beyond their relatively fully extended positions, arm 15 and link 13 forming an obtuse angle when bell-crank lever 15, 16 reaches the end of its swivel deflection. Specific preferred angular values between the positions of arm 15 and link 13 will be given somewhat later. The achieved advantage is that the working pressure will be taken up by the crank 2 in dead centre position, and that at an earlier or later instant said pressure will be transmitted to the fixed fulcrum 31) in virtue of arm 15 and link 13 being relatively full extended, so that other members are relieved of this load.

If the arrangement provides for arm 15 and link 13 swinging slightly beyond their fully extended positions, then these members will pass twice through their fully extended positions whilst the ram is near its bottom dead centre. The timing of these positions in relation to the bottom dead centre of crank 2 and the fully extended position of the knee joint protects the driving members from the working pressure during an extended part of the operative ram stroke.

In such an arrangement the twoarms 1 and 4 may also be arranged at a relative angle, thus permitting the forces acting on hinge 12 to be kept fairly low, and at the same time fulcrum 30 to be located rather close to shaft 1. Consequently the entire mechanism for operatirrg the press ram may be accommodated within a small space and the head of the press may be compact and small.

In FIG. 5 the positions of the several members of the linkage are shown in full lines at the time when the ram is at top dead centre, whereas their positions are shown in discontinuous lines at the time the ram is at bottom dead centre.

It should be noted that, according to one of the novel and inventive features of the present invention, the crank 2 will be substantially at bottom dead center when the link 13 and the arm 15 form an angle ranging between 155 and 180 degrees with respect to one another. It is also characteristic of the invention that the aforementioned link 13 and arm 15 are deflected beyond the fully extended position, so as to form an angle of between 179 and 155 degrees with respect to one another, when the ram is at the lower dead center of its reciprocation.

What is claimed is:

1. In a linkage for a drawing press having a rotatable crankshaft, a first crank secured thereto, a reciprocable ram, a first arm pivotally connected to said first crank and a second arm having one end pivotally connected to said ram and a second end hingedly connected to said first arm so as to form a knee joint therewith, the improvernent comprising an extension arm rigid with said first arm, defining therewith an obtuse angle and extending beyond the pivot point between the latter and said first crank, the distance between the hinge of said knee joint and the remote end of said extension arm being smaller than twice the length of said first arm, and drive means connected between said first crank and said remote end of the extension arm, and operative to impart to said knee joint a supplemental motion in a direction substantially perpendicular to a line connecting said first crank and said ram.

2. In a linkage for a drawing press having a rotatable crankshaft, a first crank secured thereto, a reciprocable ram, a first arm pivotally connected to said first crank and a second arm having one end pivotally connected to said ram and a second end hingedly connected to said first arm so as to form a knee joint therewith, the improvement comprising an extension arm rigid with said first arm and extending beyond the pivot point between the latter and said first crank, the distance between the hinge of said knee joint and the remote end of said extension arm being smaller than twice the length of said first arm, and drive means connected to said remote end of the extension arm and operative to impart to said knee joint a supplemental motion in a direction substantially perpendicular to a line connecting said first crank and said ram, wherein said drive means includes a cam disc keyed to and driven by said crankshaft, a first link articulated at said remote end and a pivotable twoarmed lever connected between said first crank and said first link, at least one arm of said two-armed lever being oscillated by said cam disc.

3. In a linkage for a drawing press, the improvement according to claim 2, wherein the free arm of said twoarmed lever is the follower lever of said cam disc.

4. In a linkage for a drawing press having a rotatable crankshaft, a first crank secured thereto, a reciprocable ram, a first arm pivotally connected to said first crank and a second arm having one end pivotally connected to said ram and a second end hingedly connected to said first arm so as to form a knee joint therewith, the improvement comprising an extension arm rigid with said first arm and extending beyond the pivot point between the latter and said first crank, the distance between the hinge of said knee joint and the remote end of said extension arm being smaller than twice the length of said first arm, and drive means connected to said remote end of the extension arm and operative to impart to said knee joint a supplemental motion in a direction substantially perpendicular to a line connecting said first crank and said ram, wherein said drive means includes a first link articulated at said remote end, a first two-armed lever connected to said first link and pivotable about a fixed fulcrum, and a second link hingedly connected between the free arm of said first two-armed lever and said pivot point of the etxension arm so as to form a toggle joint with the latter.

5. In a linkage for a drawing press, the improvement according to claim 4, wherein the drawing press also has a reciprocable blank holder slide and auxiliary drive means connected between the latter and said drive means for simultaneous operation with said first twoarmed lever, said auxiliary drive means including an additional arm rigid with said first two-armed lever, for actuating said slide in predetermined relation to the movements of said ram.

6. In a linkage for a drawing press, the improvement according to claim 5, wherein said auxiliary drive means further includes a second and a third pivotable twoarmed lever, a third link articulated between said additional arm and said second two-armed lever, and a forth link articulated between said second and said third twoarmed levers.

7. In a linkage for a drawing press, the improvement according to claim 4, wherein said second link is articulated at a pivotal point other than said pivot point between said first arm and said first crank.

8. In a linkage (for a drawing press, the improvement according to claim 7, wherein the drawing press also has a second rotatable crank, said second link being articulated at said second crank.

9. In a linkage for a drawing press, the improvement according to claim 8, wherein said second crank is rotated synchronously with said first crank.

10. In a linkage for a drawing press, the improvement according to claim 9, wherein said second crank is secured to said crankshaft in an angularly spaced relationship with respect to said first crank.

11. In a linkage for a drawing press, the improvement according to claim 8, wherein said first link and the cooperating arm of said first two-armed lever articulated thereat are in substantially fully extended position with respect to one another when said ram is at the upper dead center of its reciprocation.

12. In a linkage for a drawing press, the improvement according to claim 11, wherein said first crank is substantially at bottom dead center when said first link and said co-operating arm of the first two-armed lever form an angle of between and degrees with respect to one another.

13. In a linkage .for a drawing press, the improvement according to claim 12, wherein said knee joint is substantially fully extended when said first crank is at said bottom dead center.

14. In a linkage for a drawing press, the improvement according to claim 8, wherein said first link and the cooperating arm of said first two-armed lever articulated thereat are deflected beyond the fully extended position so as to form an angle of between 179 and 155 degrees with respect to one another when said ram is at the lower dead center of its reciprocation.

15. In a linkage for a drawing press, the improvement according to claim 14, wherein said first two-armed lever is at the end of its pivoting motion when said ram is at said lower dead center.

References Cited by the Examiner UNITED STATES PATENTS 308,653 12/ 1884 Clemson 7440 883,024 3/1908 Humpert 7438 X 1,996,617 4/ 1935 Hahn 7440 2,005,000 6/ 1935 Miller 74---40 2,169,289 8/ 1939 Robbins et a1. 7440 2,530,715 11/1950 Mensman 7440 X 2,550,061 4/ 1951 Glasner et a1. 113-38 2,550,063 4/ 1951 Johansen 113-38 2,688,296 9/1954 Danly et a1. 11338 FOREIGN PATENTS 222,232 5/ 1910 Germany. 578,000 6/ 1933 Germany.

13,480 1903 Great Britain. 689,899 4/1953 Great Britain.

BROUGHTON G. DURHAM, Primary Examiner.

MILTON KAUFMAN, Examiner. 

1. IN A LINKAGE FOR A DRAWING PRESS HAVING A ROTATABLE CRANKSHAFT, A FIRST CRANK SECURED THERETO, A RECIPROCALBE RAM, A FIRST ARM PIVOTALLY CONNECTED TO SAID FIRST CRANK AND A SECOND ARM HAVING ONE END PIVOTALLY CONNECTED TO SAID RAM AND A SECOND END HINGEDLY CONNECTED TO SAID FIRST ARM SO AS TO FORM A KNEE JOINT THEREWITH, THE IMPROVEMENT COMPRISING AN EXTENSION ARM RIGID WITH SAID FIRST ARM, DEFINING THEREWITH AN ABTUSE ANGLE AND EXTENDING BEYOND THE PIVOT POINT BETWEEN THE LATTER AND SAID FIRST CRANK, THE DISTANCE BETWEEN THE HINGE OF SAID KNEE JOINT AND THE REMOTE END OF SAID EXTENSION ARM BEING SMALLER THAN TWICE THE LENGTH OF SAID FIRST ARM, AND DRIVE MEANS CONNECTED BETWEEN SAID FIRST CRANK AND SAID REMOTE END OF THE EXTENSION ARM, AND OPERATIVE TO IMPART TO SAID KNEE JOINT A SUPPLEMENTAL MOTION IN A DIRECTION SUBSTANTIALLY PERPENDUCULAR TO A LINE CONNECTING SAID FIRST CRANK AND SAID RAM. 